Standard molding base



ug- 30 '1949. 1.1'. QUARNs'rRoM STANDARD MOLDING BASE 2 Sheets-Sheet l Originall Filed July 21, 1943 rrd/mex Aug. 3o,- 1949. l' T. QUARNSTROM 2,480,605

S TANDARD MOLDING BASE Original Filed July 2l, 1945 2 Sheets-Sheet 2 III 46' l f1 28- s? 27 [4. 5] 26 INVNTOR.

/M 7 QUNSTOM BY l Patented Aug. 30, i949 UNITED. STATES TENT OFFICE @riginal application July 21, 1943, Serial No. 495,791. Divided and this application March 21, 1946, Serial No. 656,038

3 Claims. l

This invention relates to a mold base .employed for plastic injectio-n molding, and more particularly to combination dowel and leader'pins employed in conjunction with the mold base, as set out in co-pending application Serial No, 495,791 filed July 21, 1943, now Patent No. 2,398,893, of which the present application is a divisional part.

Heretofore in mold bases of this 'type numerous dowel pins and screws or studs have been utilized for holding the various portions of the mold base together and in proper alignment.

It is the purpose of this invention to eliminate most of these pins and screws, substituting merely a plurality of combination dowel and leader pins for accomplishing the same purpose.

It is the further purpose herein to utilize said dowel pins also as guide means for the reciprocablc injector plate for providing smooth no-nbinding movement thereof within the mold base.

This invention therefore relates to the various elements and their combinations as more fully described in conjunction with the accompanying drawings of which:

Fig. 1 is an elevational view of the mold base.

Fig. 2 is a partially sectioned plan view thereof, with iront cavityretainer and anchor plates removed.

Fig. 3 is a fragmentary elevational section thereof.

It will be understood that said drawings are merely illustrations of preferable embodiments of the invention, and that other embodiments are also contemplated within the scope oi the invention hereinafter described and claimed.

Referring to the drawings Figs. 1 and 3 show the standard mold base having a rectangular anchor plate Il with two parallels I2 and I3 dis posed thereon and secured thereto in spaced relation. Said parallels are placed inwardly of the sides of anchor plate l! to provide extending portions I4 and I5 to permit clamping thereof to a molding machine.

A back-up plate I6 rectangular in shape is positioned upon the top edges of parallels i2 and I3 providing means for supporting the removable and interchangeable rear cavity retainer plate Il. A corresponding front cavity retainer plate I8 is provided similar in shape to said rear cavity 4plate for compressive cooperative engagement with respect thereto. Both the upper surface lll of retainer plate I1 and the lower surface 20 of retainer plate I3 are blank, but are adapted to have impressed or cut therein, or inserted therein, corresponding and mating molds and cores within which is injected a plastic material to be molded therein, in the manncrhereafter set out.

Another anchor plate 23 corresponding to anchor plate il is suitably secured to the front cavity plate lil and similarly the edges 2dV and 25 of plate 23 extend beyond the edges of plate I8 to permit clamping thereof within a, molding machine.

A rectangular ejector plate is indicated at 2S longitudinally disposed between the'two parallels l2 and i3 and adapted for manually actuated upward sliding movement therebetween. A sec` ondary ejector plate 2l secured upon ejector plate itis adapted to retain and secure in upright position at right angles thereto the push back pins 2B and 20.

Ejector pins 30 and Si are shown in Fig. l as also secured by the secondary ejector plate 2l to the ejector plate 2li, so as to upwardly extend through openings in the back up plate l5 and also into openings within the core 32. The latter is positioned by the mold maker within the rear cavity plate Il in corresponding and cooperating aligned relation to the mold 33 which is also positioned within the front cavity retainer plate i8.

It will be understood that the standard base shown in Fig. 1 does not initially include the ejector pins 30 and 3l which are located as desired by the mold maker to correspond with the positioning of the molds 32 and 33 within the front and rear cavity retainer plates il and i3.

It is 4contemplated also that the stock base itself makes no provision for the molds 32 and 33 or their positioning within the blanlsed front and rear cavity retainer plates, inasmuch as their shape and positioning will differ, being dependent upon the particular molding job contemplated by the mold maker.

Referring to Figs. 1 and 3 it is seen that upon outward movement of the ejector plate 25 in addition to upward movement of ejector pins '50 and 3l, a corresponding upward movement is given to the push-back pins 2% and 23 previously described. Their downward position is indicated in Fig. 1. When the two cavity retainer plates are `again brought together within a suitable molding machine the outer ends of push-back pins 28 and 2g engage the surface Se of the front cavity retainer plate i3, whereby the ejector plate 2li is forced back into neutral position..

Ln operation in carrying out injection molding the two cavity retainer plates l1 and i8 are tightly brought together and a plastic molding material is supplied through the hollow locator 31 and into the nozzle 38 as shown in Fig. l, for injection into the molds 32 and 33.

The standard base shown in Fig. l is also pro:- vded with a sprue puller 3% .which,extendsupwardly and at right angles to the ejector plate 26 and the secondary plate 21 which secures the same to said ejector plate as shown.

Said sprue puller is merely a cylindrical pin having at its outer end an irregular undercut edge 40 within which a portion of the plastic material is fed when the molding material is injected into the molds positioned within the two cavity retainer plates I1 and I8.

When the plastic material has hardened a sprue is formed interconnecting each of the molded pieces within the corresponding molds, extending also partially up into the opening within the nozzle 38 and also extending down int the portion 40 of the sprue puller 39.

The purpose of the sprue puller is to retain the sprue within the rear cavity retainer plate I1 as the same is withdrawn from the stationary retainer plate I8 and thus prevent sticking of the sprue within the nozzle opening, which might tend to damage the sprue and the molded parts connected thereto.

Fig. 1 illustrates the construction of the ejector plate 26 which is maintained initially in spaced relation to the adjacent anchor plate I I by means of the studs 4I.

For the purpose of simplicity only one mold is shown in Fig. 1 at 32 and 33 within the corresponding cavity retainer plates i1 and I8, however, it is contemplated that any number of molds may be provided therein depending upon the molding job contemplated.

Figs. 1 and 3 show the four combination dowel and leader pins or shafts 42 transversely disposed through corresponding openings in anchor plate II, back-up plate i6 and the rear cavity retainer plate I1.

Socket headed cap screws 43 are positioned through the bottom of anchor plate II, and are adapted for threaded securing engagement with the bottom ends of dowel shafts 42 and 44, whereby said shaft may be removably, but rmly held Within the mold base and particularly members I I, I6 and I1.

The upper annular collar portion 45 of shaft 42 nesting within a corresponding annular recess 4B in the rear cavity plate I1, terminates in the upwardly extending front cavity engaging member 41. Portion 41 then slidingly extends through the bushing 48 within front cavity retainer plate IB and also into a corresponding opening in the anchor plate 23.

Fig. 2 is a plan View of the mold base with the front cavity plate I8 and corresponding anchor plate 23 withdrawn, as is the case when the two retainer plates I1 and I8 are supported within a molding machine.

The upper extending portions 41 of the four doWel shafts 42 shown in Fig. 2, are thus adapted to be slidingly received by four correspondingly arranged bushings 48 disposed within suitable openings in the front cavity retainer plate I8, as the latter and its anchor plate are correspondingly brought towards the rear cavity plate I1 within a suitable molding machine.

Thus the proper alignment is obtained between the two cavity retainer plates I'I and I8 as they are brought together prior to the injection molding operation. This consequently guarantees that the core 32 disposed within cavity plate I1 will be in exact alignment with the mold 33 for receiving the molding substance.

It will be noted that the combination dowel and leader pins 42 thus accomplish the important function of maintaining all the members of the mold base in proper alignment at all times, and particularly proper alignment between the front and rear cavity plates. By their provision numerous shafts, studs, pins and dowels are eliminated.

Said combination dowel shafts also accomplish another function in providing guide means for a reciprocable ejector plate 26.

As shown in Figs. 2 and 3 ejector plate 26 has the four spaced bushings 49 disposed therethrough with their openings coinciding in alignment with the combination dowel and leader pins 42 shown ln Fig. 2 for sliding engagement therewith.

It is noted also that the ejector plate 26 is provided With four outwardly extending arcuate flanged portions 50 within which said bushings 4S are disposed. Correspondingly arcuately notched recesses 5I are also formed within the back-up plate supporting members I2 and I3 within which the ejector plate flanged :portions 50 are disposed as indicated in Fig. 2.

A plurality of guiding means are thus provided for the ejector plate 26 whereby the same slidingly engages the combination leader and dowel pins 42.

The essential purpose oi the present invention. is to provide a means for retaining the moldingbase and its constituent elements in immovable relation for the injection molding operation. And this is accomplished as shown in Fig. 3 by the combination leader and dowel pins 42, retaining studs 43, and bushings 48 disposed within the front cavity retainer plate I8.

Having described my invention reference should now be had to the claims which follow for determining the scope thereof.

I claim:

l. In a stock base for injection plastic molding, an anchor plate adaptable for attachment to the movable member of a molding machine, upright parallel members in spaced relation carried by said plate, a rear cavity retainer plate upon said parallel members, an anchor plate adapted for attachment to the stationary member of a molding machine, a front cavity retainer plate carried by said stationary anchor plate, a plurality of leader pins, each having an annular iiange inwardly of one end retainingly engaging said rear cavity retainer plate within a corresponding annular recess therein and extending therethrough, with one of its ends extending partially into said movable anchor plate within a corresponding opening therein, and a screw extending irom the opposite side of said movable anchor plate and in threaded retaining engagement with said pin, the other end of said pin extending from said rear retainer plate for cooperative sliding engagement within a corresponding co-axial recess formed within said front retainer plate.

2. In a stock base for injection plastic molding, Aa movable anchor plate, upright parallel members in spaced relation carried by said plate. a back-up plate carried by said parallel members, a rear cavity retainer plate secured upon said back-up plate, a stationary anchor plate, a front -cavity retainer plate carried thereby, a reciprocal ejector plate interposed between said parallel members intermediate said movable anchor plate and said rear cavity retainer plate, a plurality of leader pins secured to said movable anchor plate at one of their ends and disposed through said ejector plate and back-up plate, each of said pins having an annular ange inwardly of its other end retainngly engaging said rear cavity plate Within a corresponding annular recess therein, the other ends of said pins extending from said rear retainer plate for cooperative sliding engagement within co-axial recesses in said front retainer plate, said ejector plate having spaced outwardly extending arcuate flanges on its opposite sides with openings therethrough for cooperative sliding engagement with said leader pins, said parallel members having corresponding arcuate slots to receive said arcuate flanges.

3. In a stock base for plastic molding, a movable anchor plate, upright parallel members in spaced relation carried by said plate, a rear cavity retainer plate upon said parallel members, a stationary anchor plate, a front cavity retainer plate carried thereby, a reciprocal ejector plate interposed between said parallel members intermediate said movable anchor plate and said rear cavity plate, a plurality of leader pins secured to said movable anchor plate at one of their ends and disposed through spaced guide openings in said ejector plate, each pin having an annular ange inwardly of its other end retainingly engaging said rear cavity plate within a corresponding annular recess therein, the other ends of said pins extending from said rear retainer plate for cooperative sliding engagement Within `corresponding coaxial recesses formed in said front retainer plate.

IVAR T. QUARNSTROM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,618,245 Udale Feb. 22, 1927 2,227,956 Emsley Jan. 7, 1941 2,339,792 Milano Jan. 25, 1944 2,372,833 Jobst Apr. 3, 1945 OTHER REFERENCES Modern Plastics, pp. 77 and 102, May, 1941. Plastics in Engineering" by J. Delmonte, M. S. published 1940. Copy in Division 15. 

